The determination of cholesterol in the lipoprotein in the serum and the plasma is utilized mainly for the diagnosis of arteriosclerosis, cardiomyopathy and lipid abnormality analysis, and is one of important measurement items in the clinical laboratory test field. Particularly, as to the measurement of HDL cholesterol (HDL-C) and LDL cholesterol (LDL-C), a guideline has been established by Japan Atherosclerosis Society, and is one of the high-frequency measurement items. A method for the direct determination of HDL-C which may be carried out using an automated analyzer without conducting centrifugal separation operation, includes, for example, a method of detecting only HDL-C by protecting lipoproteins other than HDL using anti β-lipoprotein antibody (Patent Literature 1); a method of detecting only HDL-C using a sugar compound such as cyclodextrin derivatives and a modified enzyme (Patent Literature 2); a method using a surface-active agent which does not dissolve lipoprotein (Patent Literature 3); a method of specifically-detecting HDL-C after elimination of cholesterol in the lipoprotein other than HDL (Patent Literature 4); and a method of detecting HDL-C, in which the lipoproteins other than HDL is protected by forming complex using calixarenes (Patent Literature 5).
On the other hand, a method for the direct determination of LDL-C which may be carried out and using an automated analyzer without conducting centrifugal separation operation, includes, a method for measurement of LDL-C, after protecting the LDL with polyanion and a ampholytic surface-active agent, and eliminating cholesterol in the lipoprotein other than LDL (Patent Literature 6); a method for measurement of the LDL-C after solubilizing and eliminating only lipoprotein other than LDL using a surface-active agent (Patent Literature 7 and Patent Literature 8); and a method for measurement of the LDL-C by protecting the lipoprotein other than LDL using calixarenes (Patent Literature 9).
However, the measurement precision of these reagents is satisfiable for a specimen having lipid concentration within normal range (normolipemic specimen), but for a specimen with lipid abnormality such as, for example, high triglyceride (TG) specimen, these reagents are not exactly sufficient with respect to accuracy of the measurement value compared with those obtained by standard determination method such as UCHM method, which are in combination with the fractionation by ultracentrifugation (Ultracentrifugation-heparin-MnCl2-method), or BQ method (Beta-Quantification method). This is the present situation. In addition, a block copolymer having polyethylene glycol in main chain and the use thereof as a cosmetic have been disclosed in Patent Literature 10.    Patent Literature 1: JP-B-3446486.    Patent Literature 2: JP-B-2600065.    Patent Literature 3: JP-B-2799835.    Patent Literature 4: JP-B-3164829.    Patent Literature 5: WO98/59068.    Patent Literature 6: JP-A-2000-60600.    Patent Literature 7: JP-B-3193634.    Patent Literature 8: JP-B-3058602.    Patent Literature 9: WO98/59068.    Patent Literature 10: JP-A-2001-288233.